1. Field of the Disclosure
The present disclosure relates to an electrostatic capacitance-type position detection device that includes a contact surface, with which a pointing body such as a fingertip of an operator can come into contact, and detects the contact position of the pointing body on the contact surface.
2. Description of the Related Art
In recent years, along with the popularization of mobile terminals such as notebook-size personal computers (notebook PCs) and cellular phones, there have been used position input devices as operation devices. In many cases, the position detection devices each including a contact surface, with which a fingertip of an operator or the like can come into contact, and detecting the contact position of the fingertip or the like on the contact surface. The position input devices are commonly used for touch pads or the like for input to personal computers, and are also applied to touch panels of portable devices, various terminal devices, and so forth, using transparent substrates and transparent electrodes.
As such position input devices, there have been electrostatic capacitance-type position input devices that each detect the contact position of a fingertip on a contact surface, based on a change in electrostatic capacitance. In a case of utilizing one of the relevant position input devices as a device for moving a cursor, a user is able to move the cursor only by gently tracing the contact surface. Therefore, the position input devices are easy to use and preferred by many users. As the related art, there has been disclosed Japanese Unexamined Patent Application Publication No. 2013-222384.
In recent years, the electrostatic capacitance-type position detection devices mounted in notebook PCs and so forth have been desired to grow in size and be reduced in price. In order to satisfy such demands, it is desirable to increase the pitch of an electrode and to keep down the number of electrodes. However, there has been a problem that position detection accuracy is deteriorated if the pitch of an electrode is increased.
In an electrostatic capacitance-type position detection device including drive electrodes, detection electrodes, and ground electrodes, electrostatic capacitance between the corresponding drive electrode and the corresponding detection electrode is reduced by bringing a finger close thereto, and the reduction amount thereof is detected for each electrode, thereby detecting a position.
However, in such an electrostatic capacitance-type position detection device, there has been a problem that the point of intersection between the corresponding drive electrode and the corresponding detection electrode becomes a portion whose sensitivity is the highest and if the electrode pitch is increased, a sensitivity variation due to a position becomes large and position detection accuracy is deteriorated.
In addition, while largely functioning as a ground conductor for reducing electrostatic capacitance between the corresponding drive electrode and the corresponding detection electrode, the pointing body such as a finger also largely functions as a floating conductor that increases the electrostatic capacitance between the corresponding drive electrode and the corresponding detection electrode. This function as the floating conductor causes a detection error (inversion sensing error), and poses an obstacle to the enhancement of detection accuracy.
The present invention solves the above-mentioned problems, and provides an electrostatic capacitance-type position detection device capable of suppressing the variation of position sensitivity and the inversion sensing error and obtaining high position detection accuracy in a case of increasing the electrode pitch.